A team from Thomas Jefferson University in Philadelphia found that Medicare reimbursed 279.4% more musculoskeletal ultrasound studies in 2008 than they did in 2000. And nonradiologists, sparked by a surge in utilization by podiatrists, accounted for 71% of the more than 157,000 increase in utilization.

"Self-referral may be contributing to higher increases of nonradiologist musculoskeletal ultrasound utilization," said presenter Richard Sharpe, MD. "These studies, if that were the case, may then not represent an efficient allocation of healthcare dollars."

Musculoskeletal ultrasound is an emerging radiology subspecialty, and utilization has increased rapidly. In fact, utilization has risen so sharply that insurers in four states -- Illinois, New Mexico, Oklahoma, and Texas -- for a time denied all claims for nonoperative spinal and musculoskeletal ultrasound, declaring the studies to be "experimental." That policy was rescinded in February 2010, however.

To document trends in musculoskeletal ultrasound utilization in the Medicare population, the researchers obtained source data from the U.S. Centers for Medicare and Medicaid Services (CMS) Part B Physician/Supplier Procedure Summary Master Files from 2000 to 2008. The data cover all Medicare fee-for-service beneficiaries and omit HMO enrollees.

To determine imaging volume, the researchers tabulated global claims and professional-component-only claims. Technical-component-only claims were excluded due to the possibility of double counting, Sharpe said.

The researchers found that 213,425 musculoskeletal ultrasound studies were primarily reimbursed by Medicare in 2008, up 279.4% from the 56,254 exams reimbursed in 2000. This also yields a 256.7% growth in utilization rate, which climbed from 171/100,000 Medicare beneficiaries in 2000 to 610/100,000 in 2008.

Of the 157,171 increase in studies over the time period, 111,268 (71%) were from nonradiologists.

"The podiatrists, which began the study as a lower user, are now using nearly as many studies as radiologists -- in just the past eight years," Sharpe said.

In other findings, the researchers noted that office (i.e., privately owned facilities) claims increased 635.8% in the study period, climbing from 19,372 in 2000 to 145,542 in 2008. Podiatrists submitted 66,103 (46.4%) of these claims, while rheumatologists contributed 22,220 (15.6%) and radiologists generated 19,390 (13.6%).

"The greatest increases in utilization occurred in private offices, and the nature of private offices is that some of these studies may be less scrutinized -- may be subject to less peer review, less validation, and less regulation," Sharpe said. "Consequently, these examinations may have wide ranges of quality."

The study team also discovered significant geographic variation by CMS region in the use of musculoskeletal ultrasound.

"In Kansas City, for example, about 20% of musculoskeletal studies are performed by nonradiologists," he said. "But in Atlanta, Dallas, New York, and San Francisco, that number is about 65%."

In addition, nearly all regions experienced significant increases in nonradiologist use of ultrasound.

"Only in Boston have nonradiologists used less [over the course of the study]," he said.

The researchers acknowledged a number of limitations of their research, including the lack of assessment of the quality or clinical appropriateness of individual ultrasound examinations. In addition, the study only evaluated the Medicare population, Sharpe said.